Pneumatic pogo stick

ABSTRACT

A pneumatic pogo stick is comprised of an elongate cylindrical housing which forms a cylinder. The housing is formed from a clear polycarbonate plastic. A top cap is attached to one end of the housing to form the top of an air chamber. A plastic piston, slidable within the cylinder, forms the bottom of the air chamber. An elongate shaft is coupled to the bottom of the piston and is moveable therewith, extending from the distal end of said housing as the piston moves within the cylinder. A bottom bracket assembly is attached to the bottom of the housing and a bushing for maintaining the lateral position of the shaft relative to the housing is attached to the bottom bracket assembly. The bushing prevents the shaft from rotating relative to the housing. User foot supports are also attached to the bottom bracket for supporting the feet of the user and handle bars are attached to the top cap for grasping with the hands of a user.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/278,075,filed Oct. 21, 2002, which claims the benefit of U.S. ProvisionalApplication No. 60/335,524, filed Oct. 19, 2001.

BACKGROUND

1. Field of the Invention

The present invention related generally to a pogo stick, and morespecifically, to a pneumatic pogo stick that utilizes lightweight anddurable materials to maximize the performance and reliability of apneumatic pogo stick.

2. Background of the Invention

A conventional pogo stick utilizes a coil spring within a hollow tubehousing to create an upward force when compressed by a user to propelthe user in an upward direction. In order to get more lift than can beprovided with a coil spring and without increasing the weight of thepogo stick itself, it has been recognized in the art that an air filledcylinder/piston arrangement can produce increased propulsion or lift forthe same length of stroke. Some have gone so far as incorporating enginepower in order to increase lift and provide a powered jumping stick.

Various attempts have been made in the art to provide pneumatic pogosticks. For example, PCT Application WO9961111 discloses an air-typepogo stick which includes an air cylinder to which foot-boards areattached in a body. The air cylinder has a valve through which a usercan regulate air. The pogo stick is simultaneously worked by both airpressure power and vacuum power created in the upper and lower part ofthe piston in the cylinder respectively when exerted by an outsideforce. Such a pogo stick, however, has many shortcomings in bothconstruction and functionality and fails to address any of the problemsencountered when attempting to use compressed air as a spring, such assmoothness of rebound.

A similar dual chamber jumping device is disclosed in U.S. Pat. No.4,632,371 in which a working cylinder provides a working chambercontaining a mass of gas. A gas exchange chamber is fixed with respectto the working cylinder. An exchange passage connects the workingchamber and the gas chamber. A gas exchange valve is provided in theexchange passage. An exchange operating handle is provide separate fromthe plunger. Such a device is overly complicated and requires multiplecomplex parts for assembly and operation. Furthermore, such a device isrelatively heavy and therefor decreases the lift capabilities of such adevice.

Thus, it would be advantageous to provide a pneumatic pogo stick that isof relatively lightweight construction, durable, safe, simple, andreliable in operation.

It would be a further advantage of the present invention to provide apneumatic pogo stick that provides a relatively smooth ride especiallyat the bottom of the compression cycle to prevent jarring of the rider.

It would be a further advantage of the present invention to provide apneumatic pogo stick that allows a user to view the internal componentsof the pogo stick for verification of the integrity of the workingparts.

It would be yet a further advantage of the present invention to providea pneumatic pogo stick that is capable of smoothly propelling a userseveral feet off the ground.

It would be still a further advantage of the present invention toprovide a pneumatic pogo stick that is easier to maneuver than otherpogo sticks known in the art and that can be easily adjusted toaccommodate users of various weights and abilities.

These and other advantages will become apparent from a reading of thefollowing summary of the invention and description of the illustratedembodiments in accordance with the principles of the present invention.

SUMMARY OF THE INVENTION

The present invention comprises a pogo stick that utilizes a pneumaticspring. The pogo stick of the present invention includes apiston/cylinder with user graspable handles attached or coupled relativeto the top of the cylinder and an elongate shaft attached to the bottomof the piston. When a user compresses air in the cylinder by jumping onfoot supports attached or coupled relative thereto, the pistoncompresses air inside the cylinder. Thus, stepping or jumping on thefoot supports pushes the piston upward, compressing the air inside thecylinder. This compressed air acts like a spring creating a force on thepiston thus forcing the piston and the attached shaft away from thehandles, which in turn propels the cylinder, the foot supports attachedthereto, and, ultimately, the user.

Such a pneumatic pogo stick has a potentially higher power to weightratio than a comparable coil spring pogo stick. Moreover, since the airpressure within the cylinder can be adjusted to accommodate the weightof a particular rider and because the compressed column of air withinthe cylinder can create tremendous force on the piston, the pneumaticpogo stick of the present invention can be configured to propel an adultuser six feet or more into the air.

The pogo stick, in accordance with the principles of the presentinvention, includes an outer housing which forms the cylinder. Thepiston is fitted within the housing and sealed relative to the insidesurface of the housing as with a U-cup seal. The piston is thus slidablewithin the housing to form the piston cylinder arrangement of thepresent invention. The housing or cylinder is formed from a plastictube, such as poly vinyl chloride (PVC) or polycarbonate. Such materialsexhibit properties of significant tensile and shear strength while beinglightweight and capable of exhibiting such properties when formed into athin-walled structure. The top of the cylinder is sealed to allow thepiston to compress an amount of air between the top of the piston andthe top of the cylinder.

In one embodiment of the present invention, the top of the cylinder issealed with a top cap member coupled to the top portion of the cylinder.Because of the extreme pressures within the cylinder that may begenerated by a user during use of the device, the top cap is configuredto be attached in a manner that securely secures the top cap to the topof the cylinder.

Handle bars or other gripping members are secured at or near the topportion of the cylinder as by coupling to the top cap. Foot supportstructure such as foot pegs are attached at or near the bottom of thecylinder. A shaft fixedly attached to the bottom of the piston extendsout the bottom of the cylinder. A rubber or urethane pad is attached tothe bottom of the shaft. As a user jumps on the pogo stick of thepresent invention, the impact between the ground and the bottom of theshaft forces the piston toward the top of the cylinder thus increasingthe air pressure within the cylinder. As the air pressure within thecylinder increases, the user decelerates until the force created by thecompressed air equals the force applied by the user to the foot pedalsand handle bars. Once the user's downward momentum is stopped, the forcegenerated by the compressed air between the piston and the top of thecylinder reverses the direction of the momentum of the user. Thecompressed air then forces the piston toward the bottom of the cylinder,rapidly extending the shaft out the bottom of the cylinder andpropelling the user and the pogo stick.

While various pneumatic pogo sticks have been attempted in the art, thepogo stick of the present invention incorporates various novel features,not the least of which is the use of a plastic material, such as a PVCor polycarbonate tube, or other plastic materials known in the art thatare strong, durable and resilient. Such strength, durability andresiliency allow the cylinder to withstand the rigors of use withoutsignificant damage or failure, including, but not limited to, severeside impact and high internal pressure. Polycarbonate is a good choicebecause it can be formed into the desired shape, has a relatively hightensile strength and is light weight. Furthermore polycarbonate can bemanufactured in a variety of colors including clear and can be easilyextruded into the desired form. Moreover, such plastic materials can bemade to be clear or at least of limited opacity so as to allow a user toview the internal workings of the pogo stick, specifically the piston,seals and other internal components to evaluate their integrity withouthaving to disassemble the device. In addition, the use of a clearmaterial for the housing allows the user to easily evaluate thecondition of the inside surface of the cylinder. Such evaluation wouldbe more difficult if the cylinder were formed from an opaque material.Those of skill in the art will appreciate that other materials may alsobe employed such as various forms of cellulose acetate butyrate, andcarbon fiber/resin/epoxy combinations.

The pogo stick of the present invention is designed to be strong anddurable while minimizing weight. In addition, it is designed to bemaneuverable and controllable during use. One feature that improvesmaneuverability and control is the use of a non-circular slider shaftengaging with a non-circular aperture at the bottom of the cylinder tolimit and/or prevent rotation of the slider shaft relative to thecylinder. In one embodiment, the slider shaft is comprised of a hollowsquare tube. In any event, the slider shaft may comprise various othernon-circular cross-sectional shapes. The square tube engages with abottom assembly which is attached to the bottom portion of the cylinderand includes a bushing that may be formed from strong, low-frictionplastic, having a square hole formed therein for slidably receiving theslider shaft while limiting rotation of the slider shaft relativethereto. The engagement of the square slider shaft with the bushingsubstantially prevents the slider shaft and thus the piston fromrotating relative to the cylinder, providing greater control of the pogostick by the user and preventing lateral wear of the piston seal thatmay otherwise be caused by rotational movement of the piston relative tothe cylinder.

Like the outer housing, the piston body itself may be made from aplastic material such as an ultra high molecular weight polyethylene(UHMWPE) or Delrin. Such materials are durable and provide a surfacehaving a low coefficient of friction so as to reduce the amount of wearon the inside surface of the cylinder 12 during use. By using thesimilar types of material for the cylinder and piston, wear issignificantly reduced between the two components.

In the case where wear or damage does occur, the piston of the presentinvention is configured to be easily replaced. In order to replace thepiston, the bottom assembly, which may be bolted with threaded fastenersto the bottom portion of the cylinder, is removed. If necessary, thefoot supports are also removed. The piston with its attached slidershaft can then be removed from the cylinder. The piston and slider shaftcan then be disassembled so that the piston can be replaced. Othercomponents such as the slider shaft and bottom bushing can also bereplaced in a similar manner.

In order to maintain air pressure within the cylinder during use, thepiston is sealed relative to the inside surface of the cylinder. If evena small amount of air were to escape from between the cylinder and thepiston during operation, the pogo stick would eventually lose itsability to propel the user. In one embodiment, a U-cup seal is placedaround the piston in a circumferential groove therein to form a sealbetween the piston and the cylinder.

As the user is propelled off the ground, the compressed air in thecylinder rapidly forces the piston to the bottom of the cylinder. Theimpact between the bottom of the cylinder and an abutment at the base ofthe cylinder is softened by use of a shock absorbing material, such asan elastomer pad. The pad cushions the piston's impact at the bottom ofits stroke. The shock absorbing pad may be doughnut shaped to fit aroundthe slider shaft and may be attached to the top of the bushing.

In another embodiment, a coil spring or other shock absorber typestructures and materials are utilized to reduce the impact between thepiston and the bottom bushing. By preventing direct contact between thepiston and the bottom assembly, the components will be protected fromdamage that may otherwise occur.

In another embodiment, because the motion of the piston creates a vacuumbelow it on its upward stroke, it is highly likely that dust and dirtwould be drawn into the cylinder. A dust seal around the slider shaftmay be provided to allow air to flow into this space.

Likewise, a chamber or housing may be provided above the bottom assemblyinto which an oil/foam air filter is inserted. The filter material isformed to fit snugly around the slider shaft. The filter effectivelyprevents dust and dirt from entering the cylinder and significantlyreduces excess wear and damage that might otherwise occur.

The distal end of the slider shaft is provided with a pad, such as aurethane or rubber pad attached to the bottom of the slider shaft. Thepad softens the initial impact of the end of the slider shaft with theground to provide a smoother and less jarring ride for the user. Inaddition, the pad provides a ground gripping structure that allows theuser to apply side forces to the pogo stick without the slider shaftslipping from beneath the user. Thus, the pad acts as both a cushion asthe pogo stick hits the ground and a ground gripping member to allow theuser to increase maneuverability of the pogo stick without losingcontrol.

A bottom assembly is attached to the bottom of the cylinder. Thisassembly provides an abutment structure at the distal end of thecylinder for preventing the piston from exiting the cylinder. The bottomassembly also provides structure for secure attachment of user footsupports.

In one embodiment, the top cap is provided with an air valve for addingair to and releasing air from the air cylinder. The air valve allows thecylinder to be pre-pressurized before use and to customize the airpressure to the user's desires. Thus, for example, for a heavier user,more air can be added before use to provide sufficient “bounce” of thepogo stick during use for the particular user. In addition, the airwithin the cylinder can be selectively released if it is determined thatless air is desired.

In order to provide a pogo stick that is comfortable to operate by anaverage user while providing the desired bounce in the device, thedimensions of the various components of the pogo stick of the presentinvention have been optimized. That is, for each rider there is apreferred distance between the hand grips and the foot pegs for mostcomfortable operation of the pogo stick. There is an importantrelationship between the above mentioned external dimension and themaximum piston stroke length. For example, for an average adult rider, astroke length of the piston of approximately 14 inches to 20 inches isdesired. Longer stroke lengths mean that the cylinder of the pogo stickmust also be longer causing the pogo stick to become longer and moreawkward to operate.

The compression ratio of the air cylinder of the pogo stick also helpsto add to or detract from the comfort of use of the pogo stick. For morecomfortable operation, the air cylinder compression ratios are fromapproximately 2.5:1 to 4.5:1. This range helps to provide smooth jumpingand landing. Furthermore, it prevents a “hammering” effect on the user,caused when the air pressure inside the air chamber ramps up rapidly dueto too high of a compression ratio. The desired compression ratio isachieved by either increasing the length of the air cylinder ordecreasing the piston stroke. The ratio of piston stroke to cylinderlength of the pogo stick of the present invention is such that this“hammering” effect is eliminated.

In one embodiment, the foot pedals include “grinding” features on theirbottom sides. Such “grinder pedals” allow the user to do tricks thatinvolve sliding on the pedals down various structures such as metalrails. These pedals may be formed from metal with plastic inserts on thebottom surface in order to decrease wear and friction when sliding.

In another embodiment, a user controllable slider shaft brake areincorporated. Such a brake allows the user to stop the motion of theslider shaft by applying a clamping or gripping force to the slidershaft. In one embodiment, a lever, such as a brake lever found on amotorcycle is provided on the handlebars for actuating the brake. Thebrake allows the user to prevent the slider shaft from moving relativeto the cylinder.

Thus, the pogo stick of the present invention has significantly morepower than a conventional spring-type pogo stick, is more maneuverable,allowing the user to perform various tricks, is durable and relativelylight weight, and is configured to provide a smooth and non-jarring ridefor a user of practically any size and weight.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe illustrated embodiments is better understood when read inconjunction with the appended drawings. For the purpose of illustratingthe invention, there is shown in the drawings several exemplaryembodiments which illustrate what is currently considered to be the bestmode for carrying out the invention, it being understood, however, thatthe invention is not limited to the specific methods and instrumentsdisclosed. In the drawings:

FIG. 1 is a cross-sectional side view of a first embodiment of apneumatic pogo stick in accordance with the principles of the presentinvention;

FIGS. 2A, 2B, 2C and 2D show first and second side views and first andsecond top views, respectively, of a first embodiment of a top cap inaccordance with the principles of the present invention;

FIG. 3 is an exploded view of a first embodiment of a bottom bracket andfoot peg in accordance with the principles of the present invention;

FIG. 4 is a partial cross-sectional side view of a first embodiment ofthe bounce pad of a pogo stick in accordance with the principles of thepresent invention;

FIGS. 5A, 5B and 5C are top and side views, respectively, of a secondembodiment of a top cap in accordance with the principles of the presentinvention;

FIGS. 6A, 6B and 6C are top, side, and cross-sectional side views,respectively, of a third embodiment of a top cap in accordance with theprinciples of the present invention;

FIG. 7A is a partial cross-sectional side view of a second piston/shaftassembly in accordance with the principles of the present invention.

FIGS. 7B and 7C are cross-sectional views of a slider shaft inaccordance with the principles of the present invention illustratingvarious geometries and orientations;

FIGS. 8A and 8B are top and side views of a second embodiment of abottom bracket/foot support assembly in accordance with the principlesof the present invention; and

FIGS. 9A and 9B are top and cross-sectional side views of a thirdembodiment of a bottom bracket assembly in accordance with theprinciples of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a first embodiment of a pneumatic pogo stick,generally indicated at 10, in accordance with the principles of thepresent invention. The pogo stick 10 is comprised of a plastic tube 12which forms an outside housing to which various other components of thedevice are attached and a cylinder portion 15 of a piston 14/cylinder 15arrangement. Plastics such as PVC or polycarbonate are preferable overother materials including steel and aluminum because they are strong,lightweight, resilient, inexpensive, and dent resistant. An alternatematerial that could be used for the cylinder 12 is cellulose acetatebutyrate. Such plastic materials are preferred since metals such asaluminum or steel, if dented, may cause the pogo stick to leak airbetween the cylinder 15 and piston 14 during use or partially or fullyobstruct movement of the piston 14 relative to the cylinder 15 so thatthe device 10 is no longer operable. Thus, despite side impacts, thecylinder 15 must remain sufficiently round in order for the piston 14 tobe able to smoothly travel through it. Because of the nature of use ofsuch an extreme pogo stick, forming the housing 12 from an easilydeformable, less resilient material may limit the life of the pogostick.

The pogo stick 10 of the present invention is configured to accommodatevarious sizes and weights of users and to propel the user several feetin the air. For example, assuming that the maximum weight of a user isabout 250 pounds and that the maximum “g” load that could be exertedwould be about 4 g's (A “g” being a measurement of acceleration where 1g equals the acceleration of gravity). For a 250 lb. user, 4 g's resultsin a 1000 lb. force or maximum load. To keep the maximum operating airpressure within the cylinder 15 at about 150 psi, the top surface of thepiston 14 would have an area of approximately 7 sq. in. or larger (1000lbs divided by 150 psi. equates to 6.67 sq. in.). A 3 inch diametercylinder 12 has an area of approximately 7 sq. in. In order to provide asafety factor, the cylinder 15 may be provided with a 3.25 inch innerdiameter. Using a 3.25 inch inner diameter cylinder 15 provides a piston14 area of approximately 8 sq. in. For a smaller user, such as a child,the diameter of the cylinder 15 may be two inches or less. Likewise, formore extreme riding and or larger adult riders, the diameter of thecylinder 15 may be four inches or more.

The thickness of the walls of the housing 12 is dependent on the type ofmaterial being used for the housing 12. The housing 12 must be able toat least withstand the 150 psi internal pressure, as well as the all ofthe various impacts and stresses that the pogo stick 10 experiencesduring use. For a polyethylene or polycarbonate housing 12, an optimalwall thickness would be about ⅛ inch. Another factor in constructing thehousing 12 is to determine an appropriate length. In order toaccommodate an average user, the length of the housing 12 should not betoo long or too short. For a rider who is approximately 5 ft. 10 inchestall, the length from foot supports 34′ and 34″ to a hand grip member 20is about 30-34 inches. If the housing 12 is to be fitted between thefoot supports 34′ and 34″ and the hand grip member 20, the length of thehousing 12 should be about 32 inches long. This length of the housing 12allows the hand grip member 20 to be positioned proximate the top of thehousing 12 and the foot supports 34′ and 34″ positioned near the bottomof the housing 12. In addition, such distance between the foot supports34′ and 34″ and the hand grip member 20 provides a comfortable positionfor the user when riding the pogo stick 10. While it is contemplatedthat longer or shorter lengths of the housing 12 could be utilized, theuse of a significantly longer housing 12 may prevent the user fromleaning over the top of the handle grip member 20 to use his/her upperbody weight to apply force to the pogo stick 10 or may extend a slidershaft 18 below the foot supports 34′ and 34″ a distance that makes itdifficult for the user to initially get on the pogo stick 10.

It is further contemplated that the foot supports could be configured tobe vertically adjustable relative to the longitudinal axis of the pogostick 10. That is, to better accommodate riders of various heights, thefoot supports 34′ and 34″ could be indirectly coupled to the bottombracket 32. For example, an outer sleeve or bracket assembly (not shown)attached to the bottom bracket 32 may provide multiple attachment pointsalong a length thereof for attachment of the foot supports 34′ and 34″at discrete locations relative to the length of the housing 12.Likewise, a riser (not shown) could be attached to the top cap to whichthe handle bars could be attached to increase the distance between thetop cap and the foot supports. As such, the distance between the footsupports 34′ and 34″ and the handle grip member 20 may be increased ordecreased depending upon the height of the user and the user'scomfortable riding position. Likewise, the handle grip member 20, whichis illustrated as being an elongate, generally straight length ofmaterial may be replaced with a handle member (not shown) that isconfigured more similarly to those found on bicycles. That is, thehandle member could have a curved or arched center portion with raisedgripping portions that extend above the point of attachment to the topof the pogo stick 10. Such a handle bar arrangement could thus beutilized to increase the effective distance between the handle gripportion and the foot supports or pedals 34′ and 34″ to accommodatetaller riders.

Compression ratio is the ratio of the volume of the air before it iscompressed, divided by the volume of the air after it is compressed. Themaximum compression ratio is, therefore, a function of the maximumstroke length and the length of the dead space that is within thecylinder 12. FIG. 1 shows the piston 14 at the top of its maximum strokeand (in dashed lines) at the bottom of its stroke. The length of strokeis in part dependent upon the total length of the cylinder 15. To alarge extent, the desired length of the pogo stick 10 is what determinesthe length of the cylinder 12, which in turn effects the diameter of thecylinder 15 to provide the desired riding characteristics of the presentinvention.

The diameter of the cylinder 12 is based on ease of use, or morespecifically, smoothness of ride and the desired feel of “springiness”generated by the compression of air in the cylinder 15. The larger thediameter of the cylinder 15, the lower the operating pressures will be.Thus, it is desirable to make the diameter of the cylinder 15 as largeas possible without making the pogo stick 10 too awkward to operate.

As the compression ratio is dependent on the stroke length, the lengthof the slider shaft 18, which is attached to the piston 14 and extendsfrom the housing 12, must be sufficient to achieve the desiredcompression ratios. While the maximum possible compression occurs whenthe shaft 18 is forced as far into the housing 12 as possible, theinsertion of the shaft 18 is limited by the amount of compressiongenerated by the particular user. Thus, the shaft 18 should besufficiently short to allow the shaft 18 to travel into the housing 12without allowing the piston 14 to contact a top cap 24, which definesthe top of the cylinder 15. The distance between the top cap 24 and thepiston 14 at the top of its maximum stroke is the “dead space” 13. Thesmaller the dead space 13, the higher the maximum compression ratio.

The length of the shaft 18 should not be so long that it causes too highof a maximum compression ratio or that a user cannot easily reach thefoot supports 34′ and 34″ when attempting to get onto the pogo stick 10.Too long of a slider shaft 18 also makes the pogo stick 10 difficult tocontrol placing the center of gravity of the user too high off theground.

In this embodiment, the top of the cylinder 12 is sealed by the cap 24that is bolted or otherwise mechanically, adhesively or chemicallyattached as by welding proximate the top 25 of the housing 12. The cap24 has an insertion portion 27 that fits tightly inside the housing 12.The cap 24 also has a lip 29 that is the approximately the samethickness as the housing wall. This lip 29 allows the cap 24 to beproperly inserted into the housing 12 during assembly as the lip 29abuts with the top of the housing 12 when the cap 24 is fully insertedtherein. The top cap 24 of the housing 12 must be sufficiently securedwithin the housing 12 so as to be able to withstand the pressure fromthe compressed air in the cylinder 15 when it is compressed by thepiston 14. An ‘O’ ring 26 in the insertion portion 27 of the top cap 24creates an airtight seal between the housing 12 and the top cap 24, withthe top cap 24 and piston 14 forming a compression chamber 17.

The handle bar 20 of the pogo stick 10 is attached by a clamp 31 that isincorporated into the top cap 24. The handle bar 20 consists of analuminum or stainless steel tube with hand grips 20′ and 20″ on bothends that extend beyond the clamp 31 of the top cap 24. The base portion33 of the top cap 24 which includes the insertion portion 27 is boltedas with threaded fasteners as shown through the wall of the housing 12and into the insertion portion 27. While only two threaded fasteners orbolts are shown, there are actually a plurality of such fastenersradially disposed around the housing 12 to provide multiple points ofattachment between the housing 12 and the top cap 24 to ensure that thetop cap 24 cannot dislodge from the housing 12.

At the distal end of the housing 12 is the bottom assembly, generallyindicated at 36. The bottom assembly 36 provides four basic functions.First, the bottom assembly 36 provides an abutment for preventing thepiston 14 from exiting the distal end of the housing 12, as when thepiston 14 is in the position shown in dashed lines. Second, the bottomassembly 36 provides structure for attaching the foot supports 34′ and34″ relative to the housing 12. Third, the bottom assembly 36 provides abearing surface for maintaining proper longitudinal alignment of theslider shaft 18 as the piston 14 moves within the cylinder 15. Fourth,the bottom assembly provides an air filtration system to filter out dustand other particulates from entering the cylinder 15 through the distalend of the housing 12. Such contaminates may otherwise form abrasives inany lubricant utilized to reduce friction between the piston 14 andcylinder 15 and thus may effect the operation of the piston/cylinderarrangement of the present invention.

The bottom assembly 36 includes a bottom bracket 32 having an insertionportion 37 similar to that of the top cap 24. The bottom bracket 36,however, has a hollow cylinder configuration for receiving andmaintaining a slider shaft bushing 38. The bushing 38 defines a centralaperture 39 for receiving the slider shaft 18 and defines a guide forthe slider shaft 18 as it moves into and out of the device. Moreover,because the slider shaft 18 has a non-circular cross-section, formingthe aperture 39 of a similar shape will prevent the slider shaft 18 fromrotating relative to the bushing 38. Furthermore, because the bottombracket 32, bushing 38 and housing 12 are bolted together with aplurality of threaded fasteners, as shown, the bushing 38 is preventedfrom rotating relative to the housing 12. It is desirable, in accordancewith the principles of the present invention, to prevent any substantialrotation of the slider shaft 18 relative to the housing 12 as the distalend of the slider shaft 40 carries the bounce pad 41. The bounce pad 41is the primary contact the user has between the pogo stick 10 and theground or riding surface. By preventing rotation of the slider shaft 18,and thus the bounce pad 41, relative to the housing 12 and thus thehandle bar 20, the rider will have more control over his or her movementby eliminating a rotational degree of freedom that would otherwise bepresent if the slider shaft were circular in cross-section. In addition,prevention of rotation of the slider shaft 18, which is coupled to thepiston 14, prevents rotation of the piston 14 relative to the cylinder15. Such rotational movement of the piston 14 relative to the cylinder15 may otherwise cause additional wear between the piston and cylinderthat would decrease the life of the device 10.

As discussed, the engagement of the external features of the slidershaft 18 with the bushing 38 substantially prevents rotation of theshaft 18. In addition, the bushing 38 is fixedly mounted relative to thehousing 12 so as to prevent rotation of the bushing 38 relative to thecylinder 12. This may be accomplished by bolting the bushing 38 into thealuminum sleeve of the bottom assembly. Another means of securing thebushing 38 to the bottom assembly may be to provide external threads onan exterior surface of the bushing 38 and internal threads on aninterior surface of the aluminum sleeve. The bushing 38 could then bethreaded into the sleeve and, if necessary, pinned in place. The bushing38 is formed from a material that has a relatively low coefficient offriction and that is resistant to wear. By having a relatively lowcoefficient of friction, the slider shaft 18 can easily glide or slidethrough the bushing 38. In addition, as previously discussed, thebushing 38 keeps the slider shaft 18 from rotating, and as such theremay be many instances during use in which the slider shaft 18 isapplying significant side lateral force to the surface of the bushing38. If the slider shaft 18 were to significantly grind against thebushing 38, the bushing 38 would wear over time, increasing the size ofthe slider hole therein such that the slider shaft 18 would be able tomove laterally relative to the bushing 38. By providing a low frictionsurface and being formed from a low wear material, the life of thebushing 38 will be significantly increased requiring less frequentreplacement, if any.

The foot supports 34′ and 34″ are fastened to the bottom bracket 32 aswith elongate bolt members.

Positioned on the top of the bottom bracket 32 and bushing 38 is adoughnut shaped air filter 42. The air filter 42 may be formed from anyfibrous material such as a felt-type pad that is capable of trappingdirt and dust entering the housing 12 through the aperture 39 of thebusing 38. On top of the air filter 42 is a shock absorbing pad 44, suchas an elastomer pad, of a similar doughnut shape for receiving theslider shaft therethrough. A coil spring or other shock absorber typestructures and materials may also be employed. By preventing directcontact between the piston 14 and the bottom assembly, the componentswill be protected from damage that would otherwise occur. The filter 42and pad 44 become sandwiched between the bottom surface of the piston 14and the top of the bottom bracket 32 and bushing 38 when the piston 14is at the bottom of its stroke, as shown in dashed lines. The pad 44thus helps absorb the impact between the piston and the bottom assembly36 to prevent damage to the various assemblies and provide a morecomfortable feel to the pogo stick 10.

As discussed, the air is compressed in the cylinder 15 as the piston 14moves toward the top cap 24. The piston 14 is cylindrically shaped andslightly smaller than the inside diameter of the cylinder 15. The piston14 may be formed from plastics such as Ultra High Molecular WeightPolyethylene or Delrin. Such materials have relatively low coefficientsof friction, high corrosion resistance, and good durability. The plasticon plastic combination of the piston 14 and the cylinder 15 creates asmoothly sliding interface allowing the piston 14 to slide along thecylinder 15 without significant wear of either component. It is alsonecessary to lubricate the inside of the cylinder 15 to reduce wear andto help seal the piston 14 relative to the cylinder 15.

The piston 14 has a circumferential groove 42 formed in its outersurface to hold a U-cup seal 43. The seal 43 can be made of Buna-Nrubber, or other materials known in the art, and creates an airtightseal between the edges of the piston 14 and the walls of the cylinder15. The seal 42 allows the piston 14 to compress the air in the cylinder15 against the top cap 24. As previously mentioned, a lubricant helps toform an airtight seal between the seal 43 and the cylinder 15.

The piston 14 of the present invention is configured to be easilyreplaceable, as may be desirable if it becomes damaged or excessivelyworn. In order to replace the piston 14, the bottom assembly, which isbolted with threaded fasteners to the bottom portion of the housing 12,is removed. If necessary, the foot supports are also removed. The piston14 with its attached slider shaft 18 is then slid from the housing 12.The piston 14 and slider shaft 18 are then disassembled so that thepiston 14 can be replaced. Other components such as the slider shaft 18and bottom bushing 36 can be replaced in a similar manner. To reassemblethe pogo stick, the slider shaft 18 and piston 14 are reinserted intothe housing 12 and the bottom assembly and foot supports reattached.

In order to maintain air pressure within the cylinder 12 during use, thepiston 14 is provided with a seal relative to the inside surface of thecylinder 15. As previously discussed, if air were to escape from thecylinder 12 during operation, the pogo stick would lose its ability topropel the user. Thus, a U-cup seal 43 provides a substantially airtightseal around the piston 14. With the seal 43 in place, a compressionchamber 17 is created between the piston 14 and the top cap 24.

As the various components are configured to be relatively easilydisassembled for replacement of parts if necessary and while the seal 43is designed to be long wearing, it may also be replaced. The seal 43 isreplaced in much the same manner that the piston 14 is replaced. Asdiscussed herein, the piston 14 is removed from the housing 12. Once thepiston 14 is outside of the housing 12, the old seal 43 is removed and anew seal then put in place. The piston 14 can then put back in thehousing 12 as is done when replacing the piston 14. Materials for theseal 43 would include rubber, EPDM, Neoprene, Silicone, Viton, PTFE, andPolyurethane. It is preferable that any such seal 43 be long wearing,resistant to UV exposure, as the housing 12 may be a clear or onlypartially opaque material, and easily replaceable.

As the user bounces in an upward direction, the piston 14 moves towardthe bottom of the cylinder 15. In one example, the piston 14 has amaximum stroke length of approximately 18 inches and there is a deadspace of approximately 8 inches at maximum stroke. This creates acompression ration of 3.25:1 which provides a relatively smooth ride forthe user. Since pressure increases inversely relative to volume, athigher compression ratios, e.g. 8:1, the pressure increases rapidly asthe piston 14 compresses the air into a much smaller space. Theresulting load doubles in the last 2 inches of travel. The result isthat the rapid increase in load at the top of the stroke has a“hammering” effect on the rider, with a great force being generated toreverse the travel of the piston 14 and rider over a very shortdistance. This reversing force acts abruptly over a very short distanceand then deteriorates rapidly.

A cylinder having an inner diameter of 3 inches to 4 inches is optimalfor an adult version of the pogo stick. If the inner diameter weresignificantly smaller, then the pressure within the air cylinder wouldhave to be proportionately increased to maintain the spring force of thepogo stick. Such an increase in pressure can produce the undesired“hammering” effect as well as requiring other modifications to thedevice, such as thicker walled materials to form the cylinder, in orderto accommodate such higher pressures.

The maximum stroke length is about 14 to 18 inches for a majority ofusers. A maximum stroke length of the piston 14 and slider shaft 18greater than 20 inches would make the pogo stick more difficult tooperate. In order to harness the pressure built up in the cylinder 15,the piston 15 is attached to the slider shaft 18. The slider shaft 18 isthe telescoping part of the pogo stick and moves up and down along withthe motion of the piston 14. The bottom of the piston 14 has a squarehole formed therein as by molding or machining. The slider shaft 18 fitsinto this hole and then is bolted or otherwise attached to the piston 14as with a shoulder bolt that runs across the diameter of the piston 14and nyloc nut. Preferably, the slider shaft 18 is made out of ChromeMoly (4130) or stainless steel tubing having a substantially square orhexagon cross-section of approximately 1.25 inch. Such materials havehigh strength to weight ratios. The slider shaft 18 thus protrudes fromthe bottom of the piston 14 and extends through the bottom bracketassembly. The bounce pad 41 formed from a material such as urethanerubber is attached to the distal end of the slider shaft 18.

Thus, forcing the shaft 18 into the housing 12 causes the piston tocompress air in the cylinder 15 to create an air spring. The higher thepsi, the larger the return force of the shaft 18 and the higher the userwill be propelled. In addition, the non-circular shape of the shaft 18and its engagement with the bottom bracket bushing 38 allows the user toapply a torque to the pogo stick since the slider shaft 18 cannot rotaterelative to the housing 12 of the pogo stick 10. This allows for morecontrol by the user. If the user inputs a rotational motion to the pogostick, the entire pogo stick will rotate allowing the user to performvarious tricks that may otherwise be difficult if the shaft 18 wereallowed to rotate relative to the cylinder 12.

FIGS. 2A, 2B 2C and 2D show a detailed view of one embodiment of a topcap, generally indicated at 124, in accordance with the principles ofthe present invention. The top cap 124 may be formed from aluminum orother suitable materials known in the art, such as a material similar toor the same as the material used for the housing. The top cap 24consists of a cylindrical bottom insertion portion 125 with an O-ringgroove 126 that plugs into and seals the top end of the housing. It isattached to the housing by use of a plurality of button head machinescrews equally spaced around the circumference, for example eight. Thehandle bar is inserted into the circular aperture 126 in the upperportion of the top cap 124 and is held in place by means of an integralclamp 128 that is tightened by two cap screws 130 and 131. The handlebars are preferably formed of lightweight aluminum tubing, similar tothat used for bicycle handlebars, or thin-wall stainless steel tubing.Such handle bars give the user significant control over the pogo stickduring use. Also included in the top cap 124 is a pressure gauge 50,fill valve 48, check valve and bleed valve 46.

In order to increase the stiffness of the pogo stick, the cylinder maybe pre-pressurized by pumping air into the compression chamber. Air isadded to the cylinder through a valve 46, such as a typical tire valvestem, attached or coupled to the top cap 124 and in fluid communicationwith the compression chamber. Air may be added by a bike pump, aircompressor, or other means, until the pressure inside the cylinderreaches a desired level. This pre-load serves to create a stiffer“spring” and allows the user to gain more height on his/her jumps. Inaddition, the pre-load also helps to decrease the possibility of theaforementioned “hammering” effect.

The air valve 46 allows adding air to and releasing air from the aircylinder. The air valve 46 allows the cylinder to be pressurized beforeuse to customize the air pressure to the user's desires. Thus, forexample, for a heavier user, more air can be added before use to providesufficient “bounce” of the pogo stick during use for the particularuser. In addition, the air within the cylinder can be selectivelyreleased if it is determined that less air is desired. This ispreferably allowed by a user activated bleed valve 48 that isincorporated into or attached to or near the handle bars. Thus, excessair pressure within the cylinder can be selectively released “on thefly.” This allows the user to reduce the “spring” of the pogo stickwhile in motion if it is determined that the cylinder is overpressurized.

The preferred embodiment of the pogo stick includes a pressure gauge 50in the top cap, thus allowing the rider to observe the pressure withinthe cylinder 12. Air pressure within the cylinder 12 reaches the gauge50 after passing through a check valve 52. This check valve 52 assuresthat the pressure gauge 50 is not subjected to continual increases anddecreases in pressure as the rider bounces on the pogo stick. It alsoallows the rider to determine the maximum pressure attained whilejumping. The aforementioned bleed valve 48 is situated so as to relievethe pressure between the check valve 52 and the pressure gauge 50.

Since the air is already under pressure, it does not compress as rapidlyand provides a smoother ride. The ability to set the pressure in thecylinder also makes it so that the pogo stick can be used by people ofdifferent weights. It allows, in essence, the stiffness of the spring tobe changed. A stiffer spring or more pre-load pressure will be used forheavier riders and less pre-load pressure will be used for lighterriders.

A desired pre-load for adult users may be in the range of 15-50 psi.Once the user is done with the pogo stick for the day, the bleed valve48 can be used to release the air within the air chamber so that theslider shaft can be inserted into the cylinder for storage of the pogostick thus decreasing the overall length of the device.

As shown in FIG. 3, a bottom bracket assembly, generally indicated at200, includes a bottom bracket 232, formed from such material asaluminum. The bottom bracket 232 is a hollow cylindrical member with aninsertion portion 233 configured to fit at least partially within thehousing. A lip 235 on the bottom bracket 232 abuts against the bottom ofthe housing. The bottom bracket assembly 200 is bolted to the housing.The bottom bracket 232 is formed to receive a UHMW or other plasticbushing 236 therein. The bushing 236 fits relatively snugly within thebottom bracket 232 and is held in place by the foot peg bolts 242. Thebushing 236 is secured to the bottom bracket 232 so as to prevent itfrom rotating and to carry the forces applied to it by the slider shaft.The bushing 236 has a hole 237 formed therein, in this case asubstantially square hole, to receive the slider shaft in a manner thatsubstantially prevents rotation of the slider shaft relative to thebushing 236. As the slider shaft slides against the bushing 236, theplastic on metal surface creates a very smooth bearing surface whileminimizing wear of the slider shaft. While not necessary, if desired, alubricant may be placed on the slider shaft.

Because the motion of the piston creates a vacuum below it on its upwardstroke, it is highly likely that dust and dirt would be drawn into thecylinder. A dust seal around the slider shaft may prevent thisoccurrence. However, since the slider shaft is not round, an effectivedust seal would be difficult to form. Therefore, a chamber or housing isprovided above the bottom assembly into which an oil/foam air filter isinserted. The filter material is formed to fit snugly around the slidershaft. This effectively prevents dust and dirt from entering thecylinder and eliminates the excess wear and damage it might cause. Thus,an air filter housing 230 is coupled to the insertion portion 233 of thebottom bracket 232 and is configured for receiving an air filter insert231 therein. The air filter insert 231 is formed from a cylindrical foampad with a square hole 239 for receiving and fitting around the slidershaft. The air filter insert 231 is positioned within the air filterhousing 230.

A shock absorbing pad 228 is positioned on top of the air filter housing230 for absorbing the shock of the piston at the bottom of its stroke.

The foot pedals 234 are attached to the bottom bracket 232 and busing236 with elongate bolts 242 that inserted through the foot pedals 234and threaded through the bottom bracket 232 and busing 236. The insidesurface 243 of the foot pedal 234 is contoured to substantially matchthe contour of the outside surface of the bottom bracket 232. As such,the foot pedal 234 is substantially prevented from rotating relative tothe bottom bracket 232 for providing a stable foot support for therider. The foot support or pedal 234 is bolted with bolt 242 into thebottom bracket 232. The pedal 234 is prevented from rotating relative tothe bolt 242 by means of the concave edge on the attaching side. Thefoot pedal 234 can be made of a variety of materials and in variousshapes and sizes to fit the particular needs of the user. Some may haveconcave arched undersides made of plastic for “grinding.”

Also, by coupling the bushing 238 to the bottom bracket 232 with thebolt 242, the bushing 236 is prevented from rotating relative to thehousing and thus can prevent rotation of the slider shaft relativethereto.

As shown in FIG. 4, the bottom 250 of the slider shaft 218 is providedwith a bounce pad 238. The bounce pad assembly 238 consists of a metalbolt portion 252 with a large round head portion or insert 256. Aurethane rubber pad 238 is bonded or mechanically attached to the insert256. The threaded portion 252 of the bounce pad assembly 238 engageswith internal threads 258 provided in a metal insert 260 attached to thedistal end or bottom 250 of the slider shaft 218. The bounce pad 238 canthen be attached to the slider shaft 218 by threading the bolt portion252 into the insert 260. Furthermore, by making the bounce pad 238detachable, it may be easily replaced if necessary as may be the casewhen the pad 238 becomes excessively worn.

The pad 238 softens the initial impact of the end of the slider shaft218 with the ground to provide a smoother and less jarring ride for theuser. In addition, the pad 238 provides a ground gripping structure likethe tires on a car that allows the user to apply side forces to the pogostick without the slider shaft 218 slipping from beneath the user. Thus,the pad 238 acts as both a cushion as the pogo stick hits the ground anda ground gripping member to allow the user to increase maneuverabilityof the pogo stick without losing control. This bounce pad 238 is longwearing and easily replaceable. Long wearing is an important traitbecause the pogo stick is designed to be used outdoors on surfaces thatare very abrasive, such as concrete and asphalt. If the material usedfor the bounce pad 238 is too soft, it would wear away more quickly,requiring more frequent replacement. There is a tradeoff, however, inthat the pad 238 should be soft enough to provide sufficient cushion forthe user during use of the pogo stick. As such, there is some wear whenthe pad impacts and moves along the ground.

FIGS. 5A, 5B and 5C illustrate another embodiment of a top cap,generally indicated at 300 in accordance with the principles of thepresent invention. The top cap 300 is similar in configuration to thetop cap illustrated in FIGS. 2A-2D, but is of a two piece construction.The top cap 300 includes an cylinder insertion section 302 and a handlebar clamping section 304. The insertion section 302 is a generallycylindrical member defining a circumscribing sealing groove 306 forreceiving a sealing member. The bottom surface of the insertion section302 defines the top of the cylinder and defines a semi-spherical recess308. The clamping section 304 is attached to the insertion portion witha plurality of externally threaded fasteners or bolts that arethreadedly inserted into threaded bores 310, 311, 312 and 313 thatextend through the two sections 314 and 316 of the clamping section 304and into the insertion portion 302.

The clamping section 304, defined by the two clamping members 314 and316 define a transversely extending channel 320 for receiving the handlebars. The engaging surfaces between the members 314 and 316 abut oneanother along one side of the channel 320. On the other side of thechannel, the engaging surfaces 322 and 324 define a gap therein between.As the bolts are tightened around the handle bars, this gap 326 willclose to cause a clamping force around the handle bars.

A fill/bleed valve port 330 is in fluid communication with the surface308 so as to be in fluid communication with the cylinder of the pogostick. The use of two pieces as illustrated provides components that areeasily machinable and easily assembled into the top cap 300 asillustrated. The insert section 302 is provided with a pluralityradially spaced bores, such as bore 332 for receiving threaded fastenerstherein and attaching the top cap 300 to the housing of the pogo stickof the present invention.

FIGS. 6A, 6B and 6C illustrate yet another embodiment of a top cap,generally indicated at 400 in accordance with the principles of thepresent invention. The top cap 400 is similar to the top cap of FIGS.5A-5C, but is formed from a single, integral component. The top cap 400includes an insertion portion 402 and a clamping portion 404. Theclamping portion 404 defines a laterally extending gap 406 that is incommunication with a transversely extending channel 408 for receivinghandle bars. The gap 406 is closed with fasteners (not shown) that areinserted into bores 410 and 412 and engage with threaded bore 414. Aport 416 is provided for receiving a schrader valve or other similarvalves known in the art. An o-ring groove 418 is also provided forreceiving a sealing member to seal the insert portion 402 to the housingof the pogo stick. A plurality of radially spaced internally threadedbores, such as bore 420 is also provided to attached the top cap 400 tothe housing of the pogo stick.

As shown in FIGS. 7A, 7B and 7C, a piston/shaft assembly, generallyindicated at 500, in accordance with the principles of the presentinvention, is comprised of a piston member 502 and a slider shaftassembly 504. The piston member 502 is comprised of a cylindricallyshaped member, formed from a material such as ultra-high molecularweight polyethylene. A circumferential groove 506 for receiving a U-cupseal 508. A central bore 510 is configured for receiving a socket headcap bolt 512 to attach the shaft assembly 504 to the piston member 502.

The shaft assembly 504 is comprised of a circular or disk shaped plateportion 514 and a tube or shaft portion 516. The shaft portion 516 maybe attached to the plate portion 514 as by welding with a weld 518. Theplate portion 514 is center drilled and tapped to receive the bolt 512.An o-ring 520 may be placed on the bolt 512. The bolt 512 is theninserted through the piston portion 502 and threaded into the tappedhole 522. The bolt 512 holds the piston member 502 onto the plate 514 ofthe slider shaft 516. In addition, the use of a plate 514 to transferthe impact forces from the slider shaft 516 to the piston member 502distributes such forces over a larger surface area of the bottom surfaceof the piston member 502 in increase the reliability of the pistonmember 502 and the life thereof.

As illustrated in FIGS. 7B and 7C, the cross-sectional configuration ofthe slider shaft 516 may be of a hexagonal shape as shown in FIG. 7B ora square shape as shown in FIG. 7C. In either case, the orientation ofthe shape may be positioned at various angles relative to the footpedals of the device. It is further contemplated that other non-circularcross-sectional shapes, both symmetrical and asymmetrical may also beemployed.

Referring now to FIGS. 8A and 8B, there is shown a foot pedal/bottombracket assembly, generally indicated at 600, which may be formed froman integral piece of machined aluminum or cast or molded materials knownin the art. The foot pedals 602 and 604 are thus integrally formed withthe bottom bracket assembly 606. The bottom bracket assembly or portion606 is configured similarly to other embodiments described herein andcan be configured to accommodate a square slider shaft or a hexagonalslider shaft. The bracket assembly 606 is provided with a plurality ofradially spaced bores, such as bore 614 for attaching the bottom bracket606 to the housing of the pogo stick. A bushing 616′ or 616″ is coupledto the bracket assembly 606 so as to receive the slider shaft asdiscussed with reference to other embodiments herein, with the bushing616′ configured for receiving a square slider shaft and the bushing 616″configured for receiving a hexagonal slider shaft.

The foot pedals 602 and 604 are each provided with curved surfaces 620and 622, respectively, on the bottoms thereof to provide the ability ofthe user riding the pogo stick to do various other extreme maneuvers,such as grinding and the like. Thus, the foot pedals of the presentinvention may include “grinding” features on their bottom sides. Such“grinder pedals” allow the user to do tricks that involve sliding on thepedals down various structures such as metal rails. Such pedals may alsobe formed from plastic with metal inserts on the bottom surface in orderto decrease wear and friction when sliding.

As shown in FIGS. 9A and 9B, a bottom bracket assembly, generallyindicated at 700, for receiving a hex shaped slider tube is illustrated.The bottom bracket assembly 700 includes a bottom bracket 702 that issealed with an o-ring 704 to the housing 706 and attached thereto withfasteners 708 and 710. The filter housing 712 is positioned on top ofthe bracket 702 and the resilient pad 714 is positioned above the filterhousing 712. The slider shaft 716 fits within the bushing 718 and isprevented from rotation therewith. A pair of radially extending,internally threaded bores 720 and 722 are provided for attaching footsupport members as previously described.

Hydraulic brakes may also be a feature of the pogo stick. Such brakesallow the user to stop the motion of the slider shaft by applying aclamping or gripping force to the slider shaft. In one embodiment, alever, such as a brake lever found on a motorcycle is provided on thehandlebars. The brakes, which may include brake pads or engaging membersfor grasping and holding the slider shaft, allow the user to prevent theslider shaft from moving relative to the cylinder such as when, forexample, the slider shaft is not fully extended. The user can stop themotion of the pogo stick, rest for a moment, and then release the brakelaunching the user back into the air.

The pogo stick of the present invention has significantly more powerthan a conventional spring-type pogo stick, is more maneuverable,allowing the user to perform various tricks, and is durable andrelatively light weight.

While the apparatus of the present invention has been described withreference to certain illustrative embodiments to illustrate what isbelieved to be the best mode of the invention, it is contemplated thatupon review of the present invention, those of skill in the art willappreciate that various modifications and combinations may be made tothe present embodiments without departing from the spirit and scope ofthe invention as recited in the claims. For example, the top of thecylinder may be sealed off with a plastic cap that is attached to orintegrally formed with the top portion of the housing. In addition,while it has been illustrated that a clamping device is secured to orintegrated with the top cap for holding a pair of handle bars orgripping members to the top cap, the handle bars could be integrallyformed with the top cap such that the top cap and handle bars are formedfrom a single injection molded piece.

It is also contemplated that a two piece aluminum clamp may be securedaround the handle bars and then attached to the top cap. Likewise thehandle bar clamping mechanism could be formed from other materials knownin the art including polyethylene or polycarbonate. The claims providedherein are intended to cover such modifications and combinations and allequivalents thereof. Reference herein to specific details of theillustrated embodiments is by way of example and not by way oflimitation.

1. A pneumatic pogo stick, comprising: an elongate cylindrical housinghaving a proximal end and a distal end forming a cylinder, said elongatecylindrical housing formed from plastic; a top cap attached proximatethe proximal end of the housing; a piston slidable within the cylinderand forming a substantially air tight chamber between the piston,cylinder and top cap; an elongate shaft coupled to said piston andmoveable therewith extending from said distal end of said housing; abottom bracket assembly attached proximate the bottom of the housing; aguide for maintaining the lateral position of the shaft relative to thehousing as the shaft moves with the piston; at least one user footsupport coupled to the bottom bracket assembly; and at least one handgrip member coupled to said top cap.
 2. The pogo stick of claim 1,wherein said housing is formed from an at least partially transparentplastic material to allow viewing of the piston therein.
 3. The pogostick of claim 1, wherein said top cap is comprised of an insertionportion and a clamping portion, said insertion portion configured forinserting into the housing and attaching thereto and said clampingportion configured for receiving and clamping a handle member thereto.4. The pogo stick of claim 3, wherein said insertion portion includes aplurality of radially spaced bores for receiving a plurality of threadedfasteners for attaching the top cap to the housing.
 5. The pogo stick ofclaim 3, wherein said top cap includes at least one port for receiving avalve mechanism therein to allow pre-pressurization of the chamber. 6.The pogo stick of claim 1, further including a plate portion attached tosaid elongate shaft and said piston is attached to said plate portion.7. The pogo stick of claim 1, wherein said piston is formed fromplastic.
 8. The pogo stick of claim 1, wherein said elongate shaft has anon-circular cross-section, and said guide comprises a bushing having asimilarly shaped non-circular bore for receiving the elongate shafttherein and substantially preventing rotation of the elongate shaftrelative to the bushing.
 9. The pogo stick of claim 1, wherein saidbottom bracket assembly and said at least one foot support areintegrally formed.
 10. The pogo stick of claim 1, wherein said bottombracket includes a plurality of radially spaced bores for receiving aplurality of threaded fasteners for attaching the bottom bracketproximate to the distal end of the housing.
 11. The pogo stick of claim1, further including an air filter positioned between the bottom bracketand the piston.
 12. The pogo stick of claim 1, further including aresilient pad for absorbing the shock of the piston against the bottombracket.
 13. The pogo stick of claim 1, wherein a diameter of saidhousing is approximately two inches to four inches in diameter.
 14. Thepogo stick of claim 1, wherein the compression ratio of the volume ofair in the chamber before it is compressed divided by the volume of airin the chamber at maximum compression is approximately 2.5:1 to 4.5:1.15. A pneumatic pogo stick, comprising: an elongate cylindrical housinghaving a proximal end and a distal end forming a cylinder, said elongatecylindrical housing formed from an at least partially transparentplastic; a top cap attached proximate the proximal end of the housing,the top cap having an attachment portion for attaching to the housing;handle bars attached to the top cap for grasping by a user; a pistonassembly slidable within the cylinder and forming a substantially airtight chamber between the piston, cylinder and top cap; an elongateshaft having a non-circular cross-section coupled to said piston andmoveable therewith extending from said distal end of said housing; abottom bracket assembly attached proximate the bottom of the housing; abushing attached to the bottom bracket, said bushing defining anaperture of a non-circular shape similar to that of the elongate shaftfor maintaining the lateral and rotational position of the shaftrelative to the housing as the shaft moves with the piston; a pair ofuser foot supports coupled to the bottom bracket assembly; and a pair ofhandle bars attached to the top cap for grasping by a user.
 16. The pogostick of claim 15, wherein said top cap is comprised of an insertionportion and a clamping portion, said insertion portion configured forinserting into the housing and attaching thereto and said clampingportion configured for receiving and clamping said pair of handle bars.17. The pogo stick of claim 16, wherein said insertion portion includesa plurality of radially spaced bores for receiving a plurality ofthreaded fasteners for attaching the top cap to the housing.
 18. Thepogo stick of claim 16, wherein said top cap includes at least one portfor receiving a valve mechanism therein to allow pre-pressurization ofthe chamber.
 19. The pogo stick of claim 15, further including a plateportion attached to said elongate shaft, said piston attached to saidplate portion.
 20. The pogo stick of claim 15, wherein said piston isformed from plastic.
 21. The pogo stick of claim 15, wherein said bottombracket assembly and said at least one foot support are integrallyformed.
 22. The pogo stick of claim 15, wherein said bottom bracketincludes a plurality of radially spaced bores for receiving a pluralityof threaded fasteners for attaching the bottom bracket proximate to thedistal end of the housing.
 23. The pogo stick of claim 15, furtherincluding an air filter positioned between the bottom bracket and thepiston.
 24. The pogo stick of claim 15, further including a resilientpad for absorbing the shock of the piston against the bottom bracket.25. The pogo stick of claim 15, wherein a diameter of said housing isapproximately two to four inches in diameter.
 26. The pogo stick ofclaim 15, wherein the compression ratio of the volume of air in thechamber before it is compressed divided by the volume of air in thechamber at maximum compression is approximately 2.5:1 to 4.5:1.
 27. Thepogo stick of claim 15, further comprising a U-cup seal associated withsaid piston for forming a seal between said piston and said cylinder.